Industrial waste, especially in the form of hazardous metal-containing effluents, process solution dumps, and sludges, is threatening to become a major environmental contaminant. Most of the recent new technologies developed to meet this problem are aimed at destruction or stabilization, rather than recovery, of the metal values contained in such industrial wastes. Chromium is commonly found in its oxide or hydroxide +3 valence in industrial waste, along with other valuable metals such as copper, silver, cadmium, cobalt, gold, lead, nickel, tin and zinc.
Various attempts have been made using membrane-based solvent extractions to recover metal values from aqueous solutions. See, for example, U.S. Pat. Nos. 3,956,122, 3,957,504 and 4,437,994. However, such methods have not met with much success due to inadequate selectivities and flux rates, which in turn contribute to overall inefficiency. There is therefore a need in metals recovery technology for a truly efficient and economical method of recovering metal values from industrial waste waters. This need and others that will become apparent are met by the process and apparatus of the present invention.